Hi Jvanwouden,
To answer your question if you are using an iPhone with ios 7 installed:
1-Open up the Phone app at the bottom of every home screen. At the bottom of the window you should see 'Recents'. Click this. You will see a list of recent callers.
2-Click the i next to the number you wish to block. Scroll down to the bottom of the page and you will see the option to 'Block this Caller'. Click it and confirm your choice. That's it!
If you have an *Android operating system:
1-Pull up your contact list by selecting the phone icon from your home screen.
2-Then tap the three dot menu and choose Settings > Call > Call Rejection > Auto Reject List > Create.
3-At this point, Android phones will have a search box that’ll appear.
4-Insert the phone number or name of the person you want to block, and presto, that name will be added to the Auto Reject List.
*Some android versions differ, the above is with the Android version using KitKat or LoliPop
I hope this helps!
Cheers
